Add changelog command

This should be backwardscompatible with 0.0.1 json format.

Also slightly change 'getTagged' to list the latest version
with a tag, not the oldest.

app/ghcup-gen/GHCupDownloads.hs

@@ -1027,6 +1027,9 @@ ghcupDownloads = M.fromList
       [ ( [vver|7.10.3|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/7.10.3/docs/html/users_guide/release-7-10-1.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/7.10.3/ghc-7.10.3-src.tar.xz|]
               (Just [rel|ghc-7.10.3|])
@@ -1070,6 +1073,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.0.2|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.0.2/docs/html/users_guide/8.0.1-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.0.2/ghc-8.0.2-src.tar.xz|]
               (Just [rel|ghc-8.0.2|])
@@ -1113,6 +1119,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.2.2|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.2.2/docs/html/users_guide/8.2.2-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.2.2/ghc-8.2.2-src.tar.xz|]
               (Just [rel|ghc-8.2.2|])
@@ -1162,6 +1171,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.4.1|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.4.1/docs/html/users_guide/8.4.1-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.4.1/ghc-8.4.1-src.tar.xz|]
               (Just [rel|ghc-8.4.1|])
@@ -1198,6 +1210,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.4.2|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.4.2/docs/html/users_guide/8.4.2-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.4.2/ghc-8.4.2-src.tar.xz|]
               (Just [rel|ghc-8.4.2|])
@@ -1245,6 +1260,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.4.3|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.4.3/docs/html/users_guide/8.4.3-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.4.3/ghc-8.4.3-src.tar.xz|]
               (Just [rel|ghc-8.4.3|])
@@ -1291,6 +1309,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.4.4|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.4.4/docs/html/users_guide/8.4.4-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.4.4/ghc-8.4.4-src.tar.xz|]
               (Just [rel|ghc-8.4.4|])
@@ -1342,6 +1363,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.6.1|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.6.1/docs/html/users_guide/8.6.1-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.6.1/ghc-8.6.1-src.tar.xz|]
               (Just [rel|ghc-8.6.1|])
@@ -1389,6 +1413,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.6.2|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.6.2/docs/html/users_guide/8.6.2-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.6.2/ghc-8.6.2-src.tar.xz|]
               (Just [rel|ghc-8.6.2|])
@@ -1430,6 +1457,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.6.3|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.6.3/docs/html/users_guide/8.6.3-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.6.3/ghc-8.6.3-src.tar.xz|]
               (Just [rel|ghc-8.6.3|])
@@ -1481,6 +1511,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.6.4|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.6.4/docs/html/users_guide/8.6.4-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.6.4/ghc-8.6.4-src.tar.xz|]
               (Just [rel|ghc-8.6.4|])
@@ -1527,6 +1560,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.6.5|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.6.5/docs/html/users_guide/8.6.5-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.6.5/ghc-8.6.5-src.tar.xz|]
               (Just [rel|ghc-8.6.5|])
@@ -1577,6 +1613,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.8.1|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.8.1/docs/html/users_guide/8.8.1-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.8.1/ghc-8.8.1-src.tar.xz|]
               (Just [rel|ghc-8.8.1|])
@@ -1627,6 +1666,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.8.2|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.8.2/docs/html/users_guide/8.8.2-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.8.2/ghc-8.8.2-src.tar.xz|]
               (Just [rel|ghc-8.8.2|])
@@ -1677,6 +1719,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.8.3|]
         , VersionInfo
             [Recommended]
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.8.3/docs/html/users_guide/8.8.3-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.8.3/ghc-8.8.3-src.tar.xz|]
               (Just [rel|ghc-8.8.3|])
@@ -1727,6 +1772,9 @@ ghcupDownloads = M.fromList
       , ( [vver|8.10.1|]
         , VersionInfo
             [Latest]
+            (Just
+              [uri|https://downloads.haskell.org/ghc/8.10.1/docs/html/users_guide/8.10.1-notes.html|]
+            )
             (Just $ DownloadInfo
               [uri|https://downloads.haskell.org/~ghc/8.10.1/ghc-8.10.1-src.tar.xz|]
               (Just [rel|ghc-8.10.1|])
@@ -1796,6 +1844,9 @@ ghcupDownloads = M.fromList
       [ ( [vver|2.4.1.0|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/~cabal/cabal-install-2.4.1.0/changelog|]
+            )
             (Just $ DownloadInfo
               [uri|https://github.com/haskell/cabal/archive/cabal-install-v2.4.1.0.tar.gz|]
               (Just [rel|cabal-cabal-install-v2.4.1.0/cabal-install|])
@@ -1824,6 +1875,9 @@ ghcupDownloads = M.fromList
       , ( [vver|3.0.0.0|]
         , VersionInfo
             []
+            (Just
+              [uri|https://downloads.haskell.org/~cabal/cabal-install-3.0.0.0/changelog|]
+            )
             (Just $ DownloadInfo
               [uri|https://github.com/haskell/cabal/archive/cabal-install-v3.0.0.0.tar.gz|]
               (Just [rel|cabal-cabal-install-v3.0.0.0/cabal-install|])
@@ -1850,6 +1904,9 @@ ghcupDownloads = M.fromList
       , ( [vver|3.2.0.0|]
         , VersionInfo
             [Recommended, Latest]
+            (Just
+              [uri|https://downloads.haskell.org/~cabal/cabal-install-3.2.0.0/changelog|]
+            )
             (Just $ DownloadInfo
               [uri|https://github.com/haskell/cabal/archive/cabal-install-v3.2.0.0.tar.gz|]
               (Just [rel|cabal-cabal-install-v3.2.0.0/cabal-install|])
@@ -1878,17 +1935,28 @@ ghcupDownloads = M.fromList
   , ( GHCup
     , M.fromList
       [ ( [vver|0.1.4|]
-        , VersionInfo [Recommended, Latest] Nothing $ M.fromList
+        , VersionInfo
+            [Recommended, Latest]
+            (Just
+              [uri|https://gitlab.haskell.org/haskell/ghcup-hs/-/blob/master/CHANGELOG.md|]
+            )
+            Nothing
+          $ M.fromList
               [ ( A_64
                 , M.fromList
-              [ (Linux UnknownLinux, M.fromList [(Nothing, ghcup_014_64_linux)])
+                  [ ( Linux UnknownLinux
-              , (Darwin, M.fromList [(Nothing, ghcup_014_64_darwin10_13)])
+                    , M.fromList [(Nothing, ghcup_014_64_linux)]
+                    )
+                  , (Darwin , M.fromList [(Nothing, ghcup_014_64_darwin10_13)])
                   , (FreeBSD, M.fromList [(Nothing, ghcup_014_64_freebsd)])
                   ]
                 )
               , ( A_32
                 , M.fromList
-              [(Linux UnknownLinux, M.fromList [(Nothing, ghcup_014_32_linux)])]
+                  [ ( Linux UnknownLinux
+                    , M.fromList [(Nothing, ghcup_014_32_linux)]
+                    )
+                  ]
                 )
               ]
         )

app/ghcup/Main.hs

@@ -33,6 +33,7 @@ import           Data.Char
 import           Data.Either
 import           Data.Functor
 import           Data.List                      ( intercalate )
+import           Data.Maybe
 import           Data.String.Interpolate
 import           Data.Text                      ( Text )
 import           Data.Versions
@@ -85,6 +86,7 @@ data Command
   | Compile CompileCommand
   | Upgrade UpgradeOpts Bool
   | ToolRequirements
+  | ChangeLog ChangeLogOptions
 
 data ToolVersion = ToolVersion Version
                  | ToolTag Tag
@@ -126,17 +128,19 @@ data UpgradeOpts = UpgradeInplace
                  | UpgradeGHCupDir
                  deriving Show
 
+data ChangeLogOptions = ChangeLogOptions
+  { clOpen    :: Bool
+  , clTool    :: Maybe Tool
+  , clToolVer :: Maybe ToolVersion
+  }
+
 
 opts :: Parser Options
 opts =
   Options
-    <$> switch
+    <$> switch (short 'v' <> long "verbose" <> help "Enable verbosity")
-          (short 'v' <> long "verbose" <> help
-            "Enable verbosity"
-          )
     <*> switch
-          (short 'c' <> long "cache" <> help
+          (short 'c' <> long "cache" <> help "Cache downloads in ~/.ghcup/cache"
-            "Cache downloads in ~/.ghcup/cache"
           )
     <*> (optional
           (option
@@ -164,15 +168,21 @@ com =
   subparser
       (  command
           "install"
-          ((info ((Install <$> installOpts) <**> helper)
+          ((info
-                 (progDesc "Install or update GHC" <> footerDoc (Just $ text installFooter))
+             ((Install <$> installOpts) <**> helper)
+             (  progDesc "Install or update GHC"
+             <> footerDoc (Just $ text installFooter)
+             )
            )
           )
       <> command
            "set"
            (   SetGHC
-           <$> (info (setGHCOpts <**> helper)
+           <$> (info
-                     (progDesc "Set currently active GHC version" <> footerDoc (Just $ text setFooter))
+                 (setGHCOpts <**> helper)
+                 (  progDesc "Set currently active GHC version"
+                 <> footerDoc (Just $ text setFooter)
+                 )
                )
            )
       <> command
@@ -183,8 +193,11 @@ com =
 
       <> command
            "install-cabal"
-           ((info ((InstallCabal <$> installOpts) <**> helper)
+           ((info
-                  (progDesc "Install or update cabal" <> footerDoc (Just $ text installCabalFooter))
+              ((InstallCabal <$> installOpts) <**> helper)
+              (  progDesc "Install or update cabal"
+              <> footerDoc (Just $ text installCabalFooter)
+              )
             )
            )
       <> command
@@ -196,12 +209,14 @@ com =
            )
       <> command
            "upgrade"
-           (info ((Upgrade <$> upgradeOptsP <*>
+           (info
-            switch
+             (    (Upgrade <$> upgradeOptsP <*> switch
-            (short 'f' <> long "force" <> help
+                    (short 'f' <> long "force" <> help "Force update")
-              "Force update"
+                  )
+             <**> helper
+             )
+             (progDesc "Upgrade ghcup")
            )
-           ) <**> helper) (progDesc "Upgrade ghcup"))
       <> command
            "compile"
            (   Compile
@@ -222,6 +237,14 @@ com =
                          (progDesc "Show the requirements for ghc/cabal")
                    )
                )
+          <> command
+               "changelog"
+               ((info (fmap ChangeLog changelogP <**> helper)
+                      (progDesc "Find/show changelog"
+                      <> footerDoc (Just $ text changeLogFooter)
+                      )
+                )
+               )
           <> commandGroup "Other commands:"
           <> hidden
           )
@@ -240,7 +263,9 @@ com =
   "cabal install cabal-install", which installs into "~/.cabal/bin" by
   default. Make sure to set up your PATH appropriately, so the cabal
   installation takes precedence.|]
-
+  changeLogFooter = [i|Discussion:
+  By default returns the URI of the ChangeLog of the latest GHC release.
+  Pass '-o' to automatically open via xdg-open.|]
 
 
 installOpts :: Parser InstallOptions
@@ -288,19 +313,47 @@ rmOpts :: Parser RmOptions
 rmOpts = RmOptions <$> versionArgument
 
 
+changelogP :: Parser ChangeLogOptions
+changelogP =
+  (\x y -> ChangeLogOptions x y)
+    <$> switch (short 'o' <> long "open" <> help "xdg-open the changelog url")
+    <*> (optional
+          (option
+            (eitherReader
+              (\s' -> case fmap toLower s' of
+                "ghc"   -> Right GHC
+                "cabal" -> Right Cabal
+                "ghcup" -> Right GHCup
+                e       -> Left $ e
+              )
+            )
+            (short 't' <> long "tool" <> metavar "<ghc|cabal|ghcup>" <> help
+              "Open changelog for given tool (default: ghc)"
+            )
+          )
+        )
+    <*> optional toolVersionArgument
+
 compileP :: Parser CompileCommand
 compileP = subparser
   (  command
       "ghc"
       (   CompileGHC
-      <$> (info (compileOpts <**> helper) (progDesc "Compile GHC from source" <> footerDoc (Just $ text compileFooter))
+      <$> (info
+            (compileOpts <**> helper)
+            (  progDesc "Compile GHC from source"
+            <> footerDoc (Just $ text compileFooter)
+            )
           )
       )
   <> command
        "cabal"
        (   CompileCabal
-       <$> (info (compileOpts <**> helper)
+       <$> (info
-                 (progDesc "Compile Cabal from source" <> footerDoc (Just $ text compileCabalFooter))
+             (compileOpts <**> helper)
+             (  progDesc "Compile Cabal from source"
+             <> footerDoc (Just $ text compileCabalFooter)
+             )
            )
        )
   )
@@ -401,9 +454,7 @@ toolVersionArgument =
 
 
 versionArgument :: Parser Version
-versionArgument = argument
+versionArgument = argument (eitherReader versionEither) (metavar "VERSION")
-  (eitherReader versionEither)
-  (metavar "VERSION")
 
 versionParser :: Parser Version
 versionParser = option
@@ -420,7 +471,7 @@ tagEither s' = case fmap toLower s' of
 versionEither :: String -> Either String Version
 versionEither s' =
   -- 'version' is a bit too lax and will parse typoed tags
-  case readMaybe ((:[]) . head $ s') :: Maybe Int of
+                   case readMaybe ((: []) . head $ s') :: Maybe Int of
   Just _  -> bimap (const "Not a valid version") id . version . T.pack $ s'
   Nothing -> Left "Not a valid version"
 
@@ -582,7 +633,9 @@ Report bugs at <https://gitlab.haskell.org/haskell/ghcup-hs/issues>|]
 
   customExecParser
       (prefs showHelpOnError)
-      (info (opts <**> helper <**> versionHelp <**> numericVersionHelp) (footerDoc (Just $ text main_footer)))
+      (info (opts <**> helper <**> versionHelp <**> numericVersionHelp)
+            (footerDoc (Just $ text main_footer))
+      )
     >>= \opt@Options {..} -> do
           let settings = toSettings opt
 
@@ -895,6 +948,38 @@ Check the logs at ~/.ghcup/logs and the build directory #{tmpdir} for more clues
                           )
                         pure $ ExitFailure 12
 
+            ChangeLog (ChangeLogOptions {..}) -> do
+              let tool = fromMaybe GHC clTool
+                  ver' = maybe
+                    (Right Latest)
+                    (\case
+                      ToolVersion tv -> Left tv
+                      ToolTag     t  -> Right t
+                    )
+                    clToolVer
+                  muri = getChangeLog dls tool ver'
+              case muri of
+                Nothing -> do
+                  runLogger
+                    ($(logWarn)
+                      [i|Could not find ChangeLog for #{tool}, version #{either (T.unpack . prettyVer) show ver'}|]
+                    )
+                  pure ExitSuccess
+                Just uri -> do
+                  let uri' = T.unpack . decUTF8Safe . serializeURIRef' $ uri
+                  if clOpen
+                    then
+                      exec "xdg-open"
+                           True
+                           [serializeURIRef' uri]
+                           Nothing
+                           Nothing
+                        >>= \case
+                              Right _ -> pure ExitSuccess
+                              Left  e -> runLogger ($(logError) [i|#{e}|])
+                                >> pure (ExitFailure 13)
+                    else putStrLn uri' >> pure ExitSuccess
+
           case res of
             ExitSuccess        -> pure ()
             ef@(ExitFailure _) -> exitWith ef

ghcup-0.0.1.json

@@ -170,6 +170,7 @@
           "dlSubdir": "ghc-8.6.2",
           "dlUri": "https://downloads.haskell.org/~ghc/8.6.2/ghc-8.6.2-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.6.2/docs/html/users_guide/8.6.2-notes.html",
         "viTags": []
       },
       "8.0.2": {
@@ -264,6 +265,7 @@
           "dlSubdir": "ghc-8.0.2",
           "dlUri": "https://downloads.haskell.org/~ghc/8.0.2/ghc-8.0.2-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.0.2/docs/html/users_guide/8.0.1-notes.html",
         "viTags": []
       },
       "8.6.4": {
@@ -377,6 +379,7 @@
           "dlSubdir": "ghc-8.6.4",
           "dlUri": "https://downloads.haskell.org/~ghc/8.6.4/ghc-8.6.4-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.6.4/docs/html/users_guide/8.6.4-notes.html",
         "viTags": []
       },
       "8.4.1": {
@@ -482,6 +485,7 @@
           "dlSubdir": "ghc-8.4.1",
           "dlUri": "https://downloads.haskell.org/~ghc/8.4.1/ghc-8.4.1-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.4.1/docs/html/users_guide/8.4.1-notes.html",
         "viTags": []
       },
       "8.6.3": {
@@ -616,6 +620,7 @@
           "dlSubdir": "ghc-8.6.3",
           "dlUri": "https://downloads.haskell.org/~ghc/8.6.3/ghc-8.6.3-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.6.3/docs/html/users_guide/8.6.3-notes.html",
         "viTags": []
       },
       "8.10.1": {
@@ -756,6 +761,7 @@
           "dlSubdir": "ghc-8.10.1",
           "dlUri": "https://downloads.haskell.org/~ghc/8.10.1/ghc-8.10.1-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.10.1/docs/html/users_guide/8.10.1-notes.html",
         "viTags": [
           "Latest"
         ]
@@ -885,6 +891,7 @@
           "dlSubdir": "ghc-8.6.5",
           "dlUri": "https://downloads.haskell.org/~ghc/8.6.5/ghc-8.6.5-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.6.5/docs/html/users_guide/8.6.5-notes.html",
         "viTags": []
       },
       "8.4.2": {
@@ -1005,6 +1012,7 @@
           "dlSubdir": "ghc-8.4.2",
           "dlUri": "https://downloads.haskell.org/~ghc/8.4.2/ghc-8.4.2-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.4.2/docs/html/users_guide/8.4.2-notes.html",
         "viTags": []
       },
       "8.8.1": {
@@ -1132,6 +1140,7 @@
           "dlSubdir": "ghc-8.8.1",
           "dlUri": "https://downloads.haskell.org/~ghc/8.8.1/ghc-8.8.1-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.8.1/docs/html/users_guide/8.8.1-notes.html",
         "viTags": []
       },
       "8.4.3": {
@@ -1245,6 +1254,7 @@
           "dlSubdir": "ghc-8.4.3",
           "dlUri": "https://downloads.haskell.org/~ghc/8.4.3/ghc-8.4.3-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.4.3/docs/html/users_guide/8.4.3-notes.html",
         "viTags": []
       },
       "8.6.1": {
@@ -1365,6 +1375,7 @@
           "dlSubdir": "ghc-8.6.1",
           "dlUri": "https://downloads.haskell.org/~ghc/8.6.1/ghc-8.6.1-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.6.1/docs/html/users_guide/8.6.1-notes.html",
         "viTags": []
       },
       "8.8.2": {
@@ -1492,6 +1503,7 @@
           "dlSubdir": "ghc-8.8.2",
           "dlUri": "https://downloads.haskell.org/~ghc/8.8.2/ghc-8.8.2-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.8.2/docs/html/users_guide/8.8.2-notes.html",
         "viTags": []
       },
       "7.10.3": {
@@ -1618,6 +1630,7 @@
           "dlSubdir": "ghc-7.10.3",
           "dlUri": "https://downloads.haskell.org/~ghc/7.10.3/ghc-7.10.3-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/7.10.3/docs/html/users_guide/release-7-10-1.html",
         "viTags": []
       },
       "8.2.2": {
@@ -1722,6 +1735,7 @@
           "dlSubdir": "ghc-8.2.2",
           "dlUri": "https://downloads.haskell.org/~ghc/8.2.2/ghc-8.2.2-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.2.2/docs/html/users_guide/8.2.2-notes.html",
         "viTags": []
       },
       "8.4.4": {
@@ -1856,6 +1870,7 @@
           "dlSubdir": "ghc-8.4.4",
           "dlUri": "https://downloads.haskell.org/~ghc/8.4.4/ghc-8.4.4-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.4.4/docs/html/users_guide/8.4.4-notes.html",
         "viTags": []
       },
       "8.8.3": {
@@ -1983,6 +1998,7 @@
           "dlSubdir": "ghc-8.8.3",
           "dlUri": "https://downloads.haskell.org/~ghc/8.8.3/ghc-8.8.3-src.tar.xz"
         },
+        "viChangeLog": "https://downloads.haskell.org/ghc/8.8.3/docs/html/users_guide/8.8.3-notes.html",
         "viTags": [
           "Recommended"
         ]
@@ -2022,6 +2038,7 @@
           "dlSubdir": "cabal-cabal-install-v3.0.0.0/cabal-install",
           "dlUri": "https://github.com/haskell/cabal/archive/cabal-install-v3.0.0.0.tar.gz"
         },
+        "viChangeLog": "https://downloads.haskell.org/~cabal/cabal-install-3.0.0.0/changelog",
         "viTags": []
       },
       "3.2.0.0": {
@@ -2057,6 +2074,7 @@
           "dlSubdir": "cabal-cabal-install-v3.2.0.0/cabal-install",
           "dlUri": "https://github.com/haskell/cabal/archive/cabal-install-v3.2.0.0.tar.gz"
         },
+        "viChangeLog": "https://downloads.haskell.org/~cabal/cabal-install-3.2.0.0/changelog",
         "viTags": [
           "Recommended",
           "Latest"
@@ -2109,6 +2127,7 @@
           "dlSubdir": "cabal-cabal-install-v2.4.1.0/cabal-install",
           "dlUri": "https://github.com/haskell/cabal/archive/cabal-install-v2.4.1.0.tar.gz"
         },
+        "viChangeLog": "https://downloads.haskell.org/~cabal/cabal-install-2.4.1.0/changelog",
         "viTags": []
       }
     },
@@ -2149,6 +2168,7 @@
           }
         },
         "viSourceDL": null,
+        "viChangeLog": "https://gitlab.haskell.org/haskell/ghcup-hs/-/blob/master/CHANGELOG.md",
         "viTags": [
           "Recommended",
           "Latest"

lib/GHCup/Types.hs

@@ -71,6 +71,7 @@ data Tool = GHC
 -- source download and per-architecture downloads.
 data VersionInfo = VersionInfo
   { _viTags      :: [Tag]              -- ^ version specific tag
+  , _viChangeLog :: Maybe URI
   , _viSourceDL  :: Maybe DownloadInfo -- ^ source tarball
   , _viArch      :: ArchitectureSpec   -- ^ descend for binary downloads per arch
   }

lib/GHCup/Utils.hs

@@ -15,6 +15,7 @@ where
 
 import           GHCup.Errors
 import           GHCup.Types
+import           GHCup.Types.Optics
 import           GHCup.Types.JSON               ( )
 import           GHCup.Utils.Dirs
 import           GHCup.Utils.File
@@ -262,21 +263,20 @@ unpackToDir dest av = do
     ------------
 
 
--- | Get the tool versions that have this tag.
+-- | Get the tool version that has this tag. If multiple have it,
-getTagged :: GHCupDownloads -> Tool -> Tag -> [Version]
+-- picks the greatest version.
-getTagged av tool tag = toListOf
+getTagged :: Tag -> AffineFold (Map.Map Version VersionInfo) (Version, VersionInfo)
-  ( ix tool
+getTagged tag =
-  % to (Map.filter (\VersionInfo {..} -> elem tag _viTags))
+  ( to (Map.filter (\VersionInfo {..} -> elem tag _viTags))
-  % to Map.keys
+  % to Map.toDescList
-  % folded
+  % _head
   )
-  av
 
 getLatest :: GHCupDownloads -> Tool -> Maybe Version
-getLatest av tool = headOf folded $ getTagged av tool Latest
+getLatest av tool = headOf (ix tool % getTagged Latest % to fst) $ av
 
 getRecommended :: GHCupDownloads -> Tool -> Maybe Version
-getRecommended av tool = headOf folded $ getTagged av tool Recommended
+getRecommended av tool = headOf (ix tool % getTagged Recommended % to fst) $ av
 
 
 
@@ -372,3 +372,15 @@ darwinNotarization Darwin path = exec
   Nothing
   Nothing
 darwinNotarization _ _ = pure $ Right ()
+
+
+getChangeLog :: GHCupDownloads -> Tool -> Either Version Tag -> Maybe URI
+getChangeLog dls tool (Left v') =
+  preview (ix tool % ix v' % viChangeLog % _Just) dls
+getChangeLog dls tool (Right tag) = preview
+  ( ix tool
+  % getTagged tag
+  % to snd
+  % viChangeLog
+  % _Just
+  ) dls